1. Field of the Invention
The present invention relates to a method and apparatus for indicating whether an exhaust gas filter element is fully loaded.
2. Description of the Prior Art
Exhaust filter elements are utilized to filter particulates and soot from exhaust gases and in particular, diesel exhaust, to clean the exhaust gases before outletting the gases to the atmosphere. If the filters fill with soot and particulates and are fully loaded, the engine flow may be decreased substantially, caused by a build-up of excessive backpressure in the exhaust system which may cause damage to and/or decrease performance of the engine. In order to avoid damage to the engine, sensors may be utilized to measure the backpressure, so that when the pressure exceeds a predetermined amount, the operator of the equipment is signalled to indicate that the backpressure is excessive. The filter is then removed and replaced, or is regenerated so that the backpressure is brought back within an acceptable range.
The prior methods for determining when a filter element becomes fully loaded by utilizing a backpressure sensor has several flaws. For typical operations for diesel forklifts, the engines are operated at full throttle for short bursts or at idle. Therefore, when the accelerator is fully depressed, the backpressure rises substantially from the increased exhaust flow. The high pressure in the exhaust system may exceed its acceptable pressure limit for a short period well before the filter is fully loaded with soot and may indicate replacement or removal of the filter prematurely. In addition, problems also arise when the sensors are used on a variety of different pieces of equipment which have different air flows, backpressure limits and different operating parameters. Also, differences in the way the equipment is operated, such as constantly at full throttle or only occasionally at a higher RPM, may also affect what would be an acceptable performance limit.
It can be seen then, that an exhaust filter backpressure indicator is needed which does not signal false fully-loaded readings. It can also be appreciated that an indicator is needed which can be adapted to and used with a variety of different size engines and which also adapts to a variety of operating conditions.